How does an Online UPS work?

In an online UPS system the inverter section constantly powers the load during normal operation with a digitally generated AC (alternating current) sinewave supply and in almost all cases of a higher quality than would be achieved were the load to be connected directly to the mains power supply. The inverter is supplied with a DC (direct current) supply either from the front-end rectifier or battery set. This means that the UPS inverter receives either a supplier via the mains power supply (if present) or the battery set (if the mains power supply fails). The electrical capacitance built-into the inverter covers the almost instantanous transfer between DC power sources to ensure the inverter output is ‘no-break’ and truely uninterruptible.